Damping apparatus for reducing vibration of automobile body

ABSTRACT

A damping apparatus for an automobile is provided, capable of ensuring a high level of reliability while obtaining excellent damping effect with simple configuration. The damping apparatus for an automobile that reduces vibrations of an automobile body may include an actuator that is attached to the automobile body and drives an auxiliary mass; a current detector that detects a current flowing through an armature of the actuator; a section that detects a terminal voltage applied to the actuator; a calculation circuit that calculates an induced voltage of the actuator, and further calculates at least one of the relative velocity, relative displacement, and relative acceleration of the actuator, based on a current detected by the current detector and the terminal voltage; and a control circuit that drive-controls the actuator based on at least one of the relative velocity, relative displacement, and relative acceleration of the actuator calculated by the calculation circuit.

TECHNICAL FIELD

The present invention relates to a damping apparatus and a dampingcontrol method for an automobile for performing automobile vibrationsuppression control.

BACKGROUND ART

In order to improve riding feel and comfort of an automobile, there is aneed for a contrivance so that engine vibrations are not transmitted tothe driver compartment. Heretofore, there has been proposed a techniquefor reducing automobile body vibration by imparting a vibrationabsorbing function to the mounting mechanism that supports an engine, orby forced excitation with use of an actuator (for example, refer toJapanese Unexamined Patent Application, First Publication No.S61-220925, and Japanese Unexamined Patent Application, FirstPublication No. S64-083742).

In conventional techniques, in order to control an actuator, sensors areused for detecting relative displacement, relative velocity, andrelative acceleration between the actuator movable section and thefixation section. However, the sensors need to be installed in thevicinity of the engine where they are exposed to a high temperatureenvironment, and consequently there is a problem of a lack ofreliability.

Moreover, in the case of using plate springs or the like in order toensure durability of a movable element supporting means of the actuator,a resonance system is constituted by a movable section mass and platespring constant. However, in controlling automobile vibration, there isa problem of negative impact on vibration suppression control in that inthe case where the resonance magnification is high, if the resonancefrequency changes even slightly due to temperature changes or agerelated changes, the response of the actuator to command signals changessignificantly.

Also, there is known a vibration suppression apparatus that can activelyreduce vibrations of the vibration prevention target object over anentire wide frequency bandwidth by; detecting vibrations of thevibration prevention target object, passing this detection signalthrough a filter to thereby generate vibration waveforms that interferewith the vibrations of the vibration prevention target object and cancelout the vibrations, and applying signals based on these vibrationwaveforms to the actuator (for example, refer to Japanese UnexaminedPatent Application, First Publication No. H03-219140).

Control is performed to automobiles of recent years that aims to improvefuel economy by stopping cylinders of a six cylinder engine as requiredso as to drive the engine with fewer cylinders (for example, with threecylinders). If the cylinders are stopped, there is a possibility thatengine vibrations may increase compared to the vibrations in a sixcylinder operation. For solving such problems, as disclosed in JapaneseUnexamined Patent Application, First Publication No. H03-219140, avibration suppression apparatus that actively reduces vibrations acrossa wide frequency bandwidth is effective.

However, the conventional damping apparatus performs only a control tosuppress vibrations being generated. Therefore, there is a problem inthat in an automobile to which control is performed to stop apredetermined number of cylinders in a six cylinder engine, allvibrations are suppressed so that it is difficult to sense that theengine is driving, and hence the driver experiences discomfort. It isdesirable the driver experiences no discomfort, by suppressing thevibrations without letting the driver feel the switch from six cylinderdriving to a cylinder stop operation.

There is also known a vibration control apparatus for an automobile thatuses an actuator that uses reaction force occurring as a result ofdriving a movable section, to thereby generate a damping force accordingto engine revolution speed (for example, refer to Japanese UnexaminedPatent Application, First Publication No. S61-220925). According to thisapparatus, vibrations of the automobile body can be predicted from therevolution speed of the automobile engine, and a force applied to theautomobile body from the engine can be canceled by the actuator.Therefore, it is possible to reduce vibrations of the automobile body.Such a damping apparatus uses a linear actuator that performsreciprocation, to vibrate an auxiliary mass to thereby reduce vibrationsof the damping target. On the other hand, as a linear actuator, there isknown a linear actuator in which an elastic supporting section (platespring) supports a movable element at a fixed position and elasticallytransforms itself to thereby support the movable element (for example,refer to Japanese Unexamined Patent Application, First Publication No.2004-343964). In this linear actuator, no wear or sliding resistanceoccurs on the movable element, and even after use for a long period oftime, the precision of the bearing support does not decrease, and a highlevel of reliability can be attained. Furthermore, there is no powerconsumption loss caused by sliding resistance, and an improvement in theperformance can be achieved. Moreover, the elastic supporting sectionavoids interference with a coil and is supported on a stator in aposition that is away from the coil with the movable element as a basepoint. Thus, it becomes possible to arrange the voluminous coil and theelastic supporting section in close proximity to each other, andtherefore, a reduction in the size of the linear actuator can berealized.

Furthermore, there is known a damping apparatus which, in order tooptimize damping control, prepares a plurality of data maps of amplitudeand phase data according to the operating state of the automobile, andgenerates signals for driving the actuator that dampens vibrations basedon the amplitude/phase data from the data maps which is taken outaccording to the operating state of the automobile (for example, referto Japanese Unexamined Patent Application, First Publication No.H11-259147). Moreover, adaptive filters are a technique for performingdamping while following the changes in the state of an automobile, andas examples of which, there are known adaptive filters realized in timedomain (for example, refer to Japanese Unexamined Patent Application,First Publication No. H10-49204, and Japanese Unexamined PatentApplication, First Publication No. 2001-51703) and adaptive filtersrealized in frequency domain (for example, refer to “Applicationtechniques of adaptive filters”, Toshifumi Kosaka, The Journal of theAcoustical Society of Japan, volume 48, No. 7, P. 520). In any methodthat uses adaptive filters, control is performed such that the amplitudephase for suppressing vibrations is found by itself based on errorsignals (for example, acceleration signals) at a specific measuringpoint.

However, there is a problem in that since the operation of adaptivefilter processing takes a long time, the damping effect is degraded ifsudden changes occur in engine revolution speed, and in particular, themethod realized in the frequency domain takes a long time forprocessing. There is also a problem in that if there are characteristicchanges or age related changes that would cause changes in the transferfunction from the command values for the actuator to the signals at themeasuring point (acceleration), the damping characteristic is degraded.On the other hand, with the method that makes reference to the map datato perform control, processing time can be reduced and it is thereforepossible to improve response. However, there is a problem in thatindividual differences or age related changes of the actuator used forthe control or the damping target engine cause degradation in thedamping performance.

Furthermore, in the case where an auxiliary mass (weight) is attached tothe linear actuator, and the reaction force that occurs when vibratingthis auxiliary mass is used to perform damping control for suppressingvibrations of the target device, an amplitude command value andfrequency command value are found based on the vibration state value ofthe control target device, and the value of current to be applied to thelinear actuator is controlled according to this amplitude command valueand frequency command value. By attaching such a damping apparatus tothe body of an automobile, the force from the engine of the automobilebeing applied to the automobile body can be cancelled out, and thereforeit is possible to reduce vibrations of the automobile body.

However, there is a problem in that if there is occurring an externalforce (disturbance) that is close to the natural frequency determinedfrom the auxiliary mass fixed on the movable element and the platespring that holds this movable element, or if a driving command valuethat is close to the natural frequency is inputted, then excessiveamplitude occurs due to resonance, and a force greater than the requiredreaction force for damping occurs, making the linear actuator unable toperform appropriate vibration suppression control.

Moreover, there is a problem in that since there is structurallyprovided a stopper of the movable element in order to limit the movablerange of the movable element, in the case where changes in the behaviorof the automobile become significant as a result of the automobilesuddenly accelerating or traveling over a rough road surface, anexternal force acts on the auxiliary mass. Consequently, excessiveamplitude occurs so that there is a problem in that a phenomena wherethe movable element collides with the stopper occurs. Furthermore thereis a problem in that, in the case where changes in the behavior of theautomobile are significant, changes in current for driving the linearactuator also becomes more significant proportionately, and the movableelement consequently collides with the stopper. If the movable elementcollides with the stopper, the sound of collision occurs as an abnormalnoise. Also there is a problem in that if too many collisions occurbetween the movable element and the stopper, there will be a greaterchance of reduced lifetime of the components that constitute the linearactuator.

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

The present invention takes the above circumstances into consideration,and its object is to provide a damping apparatus for an automobile and acontrol method thereof, capable of ensuring a high level of reliabilitywhile obtaining an excellent damping effect with a simple configuration.

Moreover, an object is to provide a damping apparatus and a vibrationsuppression method, capable, even when the state of the excitationsource changes, of maintaining vibrations in a state the same as thatbefore the change occurred.

Furthermore, an object is to provide a damping apparatus for anautomobile and a vibration control method, capable of reducing negativeimpact of individual differences or age related changes on dampingperformance while being capable of maintaining excellent dampingperformance even for sudden changes in engine revolution speed.

Moreover, an object is to provide a damping apparatus and a controlmethod of the damping apparatus, capable of suppressing resonancephenomena and maintaining the vibration amplitude of the auxiliary masswithin an appropriate range to thereby realize ideal vibrationsuppression.

Furthermore, an object is to provide a damping apparatus and a controlmethod of the damping apparatus, capable of suppressing generation of anabnormal noise by limiting the vibration amplitude of the auxiliary masswithin an appropriate range.

Means for Solving the Problem

The present invention provides a damping apparatus for an automobilethat reduces vibrations of an automobile body, including: an actuatorthat is attached to the automobile body and drives an auxiliary mass; acurrent detector that detects a current flowing through an armature ofthe actuator; a section that detects a tet minal voltage applied to theactuator; a calculation circuit that calculates an induced voltage ofthe actuator, and further calculates at least one of a relativevelocity, a relative displacement, and a relative acceleration of theactuator, based on a current detected by the current detector and theterminal voltage; and a control circuit that controls activation of theactuator, based on at least one of the relative velocity, the relativedisplacement, and the relative acceleration of the actuator calculatedby the calculation circuit.

According to the present invention, the current flowing through theactuator that is attached to an automobile body and drives the auxiliarymass is detected, the terminal voltage applied to the actuator isdetected, then based on the detected current and the detected terminalvoltage, the induced voltage of the actuator is calculated, and at leastone of the relative velocity, relative displacement, and relativeacceleration of the actuator is further calculated, and based on atleast one of the calculated relative velocity, relative displacement,and relative acceleration of the actuator, the actuator isdrive-controlled. Therefore, for detecting the calculated relativevelocity, relative displacement, and relative acceleration between themovable section of the actuator and the fixation section, there is noneed for using sensors that are exposed to a high temperatureenvironment. As a result, a high level of reliability can be ensured.Moreover, with use of displacement information such as relativevelocity, relative displacement, and relative acceleration of theactuator, a spring effect can be obtained. Furthermore, with use ofcalculated velocity information, a damper effect can be obtained.Moreover, by performing a feed back control with use of velocityinformation (relative velocity) obtained in calculation, it is possibleto make the resonance characteristic of the actuator gradual, so thateven if the resonance frequency of the actuator changes, since the gaincharacteristic and phase characteristic are gradual, changes in responsewith respect to command signals are small, and influence on the controlperformance can be made small.

The present invention provides a damping apparatus that suppressesunwanted vibrations and generates predetermined vibrations as necessary,including: an excitation section that excites a damping target object byvibrating an auxiliary mass supported by a linear actuator; a frequencydetection section that detects a frequency of an excitation source thatoscillates the damping target object; a vibration detection section thatdetects vibrations at a measuring point; a calculation section thatfinds command values of vibrations to be suppressed and vibrations to begenerated, based on a frequency of the excitation source and a vibrationdetected at the measuring point; and a control signal output sectionthat outputs a control signal, in which the command value of vibrationsto be suppressed and the command value of vibrations to be generated aresuperimposed, to the excitation section.

According to the present invention, it is possible to suppress unwantedvibrations while generating predetermined vibrations as necessary, andtherefore there an effect can be obtained where there is no imparting ofdiscomfort associated with vibration control.

The present invention provides a damping apparatus for an automobileincluding: an excitation section that vibrates an auxiliary mass; astate information acquisition section that acquires informationindicating an operating state of an automobile; a mapping controlsection that reads out an excitation force command value according tothe operating state information acquired by the state informationacquisition section from a damping information table where the operatingstate information and a command value for generating an excitation forceby the excitation section are associated with each other, and thatcontrols the excitation section based on the excitation force commandvalue; a vibration detection section that detects a vibration statevalue indicating a vibration state of a damping target at a measuringpoint; an adaptive control section that finds an excitation forcecommand value by using an adaptive filter according to the vibrationstate detected by the vibration detection section, and controls theexcitation section based on the excitation force command value; and acontrol switching section that switches to control of the excitationsection by the adaptive control section in a case where a vibrationstate value detected by the vibration detection section exceeds apredetermined value during control of the excitation section by themapping control section.

According to the present invention, control is switched to an adaptivefilter in the case where damping control performance of the mappingcontrol is degraded due to the influence of individual differences orage related changes. Consequently, the damping performance can beimproved. Moreover, since the mapping data of mapping control is updatedaccording to the control with an adaptive filter, the dampingperformance with mapping control can be recovered. Furthermore, sincethe type is switched according to the revolution speed change rate whileperforming adaptive filter, it is possible to select an appropriateadaptive filter when changes occur to the engine revolution speed, toperform damping control. Furthermore, since the transfer functionrequired in the time domain adaptive filter is updated with thecalculation process of the frequency domain adaptive filter, it ispossible to prevent the characteristics of the time domain adaptivefilter from being degraded due to changes in the transfer function.

The present invention provides a damping apparatus that includes anactuator that drives an auxiliary mass held by spring elements, withrespect to a damping target section, and that suppresses vibrations ofthe damping target section by using a reaction force at the time ofdriving the auxiliary mass, the damping apparatus further including aresonance suppression section of the actuator based on an ideal actuatorinverse characteristic that uses a transfer function of a vibrationvelocity with respect to an excitation force of a vibrating system ofthe actuator.

According to the present invention, since there is provided theresonance suppression section of the actuator based on the idealactuator inverse characteristic that uses the transfer function of thevibration velocity with respect to an excitation force of the vibratingsystem of the actuator, it is possible to achieve an effect where theactuator characteristic can be adjusted to an arbitrary characteristicby setting the ideal actuator inverse characteristic based on a desiredcharacteristic. As a result, by increasing the damping characteristic ofthe desired characteristic, it is possible to attain a characteristicsuch that resonance in the movable section of the actuator is unlikelyto be generated by an external force that acts on the actuator mainunit. Therefore, an appropriate reaction force can be generated tothereby realize ideal vibration suppression. Moreover, since it ispossible to reduce the apparent natural frequency of the actuator byreducing the natural frequency of the desired characteristic, then evenin the vicinity of the natural frequency of the actual actuator, it ispossible to realize stable damping control without receiving theinfluence of the spring characteristic and the like. Furthermore, sinceit is possible to maintain the movable range of the movable element ofthe actuator within an appropriate range, the movable element does notcollide with the stopper. As a result, generation of collision sound canbe suppressed.

The present invention provides a damping apparatus including: anauxiliary mass member supported by a spring element; an actuator thatvibrates the auxiliary mass member; and a control section that controlsa current applied to the actuator in order to suppress vibrations of avibration damping target by using a reaction force when vibrating theauxiliary mass member with the actuator, wherein the control sectionfurther includes an amplitude amount control section that performscontrol for limiting a value of a current applied to the actuator, sothat a vibration amplitude of the auxiliary mass member does not exceeda predetermined value in a case of controlling current applied to theactuator based on an amplitude command value and a frequency commandvalue of vibrations to be generated.

According to the present invention, in the case of controlling thecurrent applied to the actuator based on the amplitude command value andthe frequency command value of the vibrations to be generated, the valueof current applied to the actuator is limited so that the vibrationamplitude of the auxiliary mass member does not exceed a predeterminedvalue. Therefore, it is possible to obtain an effect where the movableelement of the actuator can be constantly driven within an appropriatemovable range. As a result collision between the movable element and thestopper is eliminated, and hence generation of a collision sound can besuppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of an automobiledamping apparatus according to a first embodiment of the presentinvention.

FIG. 2 is a block diagram showing a configuration of a modified exampleof the first embodiment shown in FIG. 1.

FIG. 3 is a block diagram showing a configuration of an automobiledamping apparatus according to a second embodiment of the presentinvention.

FIG. 4 is a conceptual diagram showing a method of detecting an inducedelectromotive force of a linear actuator in the second embodiment.

FIG. 5 is a conceptual diagram showing a method of detecting an inducedelectromotive force of the linear actuator in the second embodiment.

FIG. 6 is diagrams showing gain characteristics and phasecharacteristics as examples of a response of the linear actuator to acommand signal (induced voltage feedback not present).

FIG. 7 is diagrams showing gain characteristics and a phasecharacteristics as examples of a response of the linear actuator to acommand signal (induced voltage feedback present).

FIG. 8 is a conceptual diagram showing a modified example of the methodof detecting an induced electromotive force of the linear actuator shownin FIG. 5.

FIG. 9 is a conceptual diagram showing a modified example of the methodof detecting an induced electromotive force of the linear actuator shownin FIG. 5.

FIG. 10 is a block diagram showing a configuration of a third embodimentof the present invention.

FIG. 11 is a block diagram showing a configuration of a fourthembodiment of the present invention.

FIG. 12 is a block diagram showing a configuration of a fifth embodimentof the present invention.

FIG. 13 is a state transition diagram showing operations of the controlswitching section 607 shown in FIG. 12.

FIG. 14 is a diagram showing a configuration of the mapping controlsection 604 shown in FIG. 12.

FIG. 15 is a diagram showing a configuration of the frequency domainadaptive filter 605 shown in FIG. 12.

FIG. 16 is a diagram showing a configuration of the time domain adaptivefilter 606 shown in FIG. 12.

FIG. 17 is a block diagram showing a configuration of an automobiledamping apparatus according to a sixth embodiment of the presentinvention.

FIG. 18 is a diagram showing a configuration of a modified example ofthe automobile damping apparatus shown in FIG. 17.

FIG. 19 is a schematic diagram showing a configuration of the excitationsection 30 shown in FIG. 17 and FIG. 18.

FIG. 20 is a block diagram showing a configuration of a seventhembodiment of the present invention.

FIG. 21 is a block diagram showing a modified example of theconfiguration of the seventh embodiment shown in FIG. 20.

FIG. 22 is a block diagram showing a configuration of an eighthembodiment of the present invention.

FIG. 23 is a block diagram showing a modified example of theconfiguration of the eighth embodiment shown in FIG. 22.

FIG. 24 is a block diagram showing a configuration of a ninth embodimentof the present invention.

FIG. 25 is a block diagram showing a modified example of theconfiguration of the ninth embodiment shown in FIG. 24.

FIG. 26 is a perspective view showing a configuration of the linearactuator.

REFERENCE SYMBOLS

30: Excitation section, 31: Linear actuator, 32: Auxiliary mass, 33:Relative velocity sensor, 40: Engine, 41: Automobile body frame, 43:Vibration sensor, 50: Upper level controller, 60: Stabilizingcontroller, 70: Power circuit

BEST MODE FOR CARRYING OUT THE INVENTION

Hereunder, preferable embodiments of the present invention aredescribed, with reference to accompanying drawings. However, the presentinvention is not limited by the respective embodiments described below,and for example, associated components of these embodiments may beappropriately combined.

First Embodiment

FIG. 1 is a block diagram showing a configuration of a damping apparatusaccording to a first embodiment of the present invention. In the presentembodiment, a case is described where the damping apparatus is appliedto an automobile as an example. In FIG. 1, reference symbol 31 denotes alinear actuator that reciprocates an auxiliary mass 32. The auxiliarymass 32 reciprocates in a direction the same as that of vibrations to besuppressed. Reference symbol 33 denotes a relative velocity sensor thatdetects a relative velocity between the linear actuator 31 and theauxiliary mass 32. Reference symbol 40 denotes an engine of anautomobile that is fixed on an automobile body frame 41. Referencesymbol 42 denotes wheels of the automobile. Reference symbol 43 denotesa vibration sensor (acceleration sensor) provided in a predeterminedposition of a passenger seat 44 or the automobile body frame 41.Reference symbol 50 denotes an upper level controller that receivesinput of engine revolution speed information such as ignition pulse,accelerator opening, and fuel injection amount from a control device(not shown in the drawing) provided in the engine 40, and an output fromthe vibration sensor 43, and outputs a driving command to the linearactuator 31 for performing damping. The upper level controller 50generates and outputs a command signal (driving command) for suppressingvibrations of the automobile body frame 41 generated by enginerevolutions. Reference symbol 60 denotes a stabilizing controller thatreceives input of a relative velocity signal output from the relativevelocity sensor 33 and a driving command output from the upper levelcontroller 50, and stably drives the linear actuator 31. Referencesymbol 70 denotes a power circuit that outputs a driving current to thelinear actuator 31, based on a stabilizing driving command output fromthe stabilizing controller 60.

The damping apparatus shown in FIG. 1 uses the reaction force thatoccurs when the auxiliary mass 32 attached to the linear actuator 31 isreciprocated, to suppress vibrations that occur in a predeterminedposition of the automobile body frame 41 or the automobile body due torevolutions of the engine 40. At this time, the stabilizing controller60 receives input of a signal of a relative velocity between the body ofthe linear actuator 31 fixed on the automobile body 41 and the auxiliarymass 32 that reciprocates, and feeds it back to a driving command. As aresult a damping force is generated for the linear actuator 31 to reducethe sensitivity with respect to disturbance vibrations that theautomobile body frame 41 receives due to uneven road surfaces. As aresult, the influence of disturbance vibrations can be reduced.

The relative velocity sensor 33 may differentiate the output of a phasesensor that detects strokes of the linear actuator 31 to thereby detectthe relative velocity. Moreover, the relative velocity sensor 33 may besuch that it detects the relative velocity from a difference betweenintegrated values from the acceleration sensors respectively provided onthe linear actuator 31 and the auxiliary mass 32.

Here, a configuration of the linear actuator (reciprocating motor) usedin the present invention is described, with reference to FIG. 26. Asshown in FIG. 26, the linear actuator includes a movable section 1, astator 2 arranged around the movable section 1, and a pair of supportingmembers (elastic supporting members) 3 having two or more superposedplate springs that support the movable section 1 and allowing themovable section 1 to reciprocate with respect to the stator 2 byelastically deforming themselves.

The movable section 1 includes a shaft 11 of a column shape having afemale screw section 11 a formed on the tip end thereof, and thatreciprocates in the axial direction, and a movable element 12 inside ofwhich the shaft 11 is inserted and which is fixed in a position partwayalong the axial direction of the shaft 11 and which serves as a movablemagnetic pole. A nut 13 for fixing the shaft 11 to a target object (notshown in the drawing) to be driven is threaded on the female screwsection 11 a.

The stator 2 includes a yoke 21, the outer shape of which seen from theaxial direction of the shaft 11 is of a rectangle shape and has nobottom end thereinside and a pair of coils 22 and 23 that are arrangedso as to have the movable section 1 therebetween and are fixed insidethe yoke 21. The coil 22 is configured such that a winding drum 26 isattached to a magnetic pole section 21 a of the yoke 21 which is formedso as to project inward, and a metal wire 27 is multiple-wound on thiswinding drum 26. The coil 23 is configured such that a winding drum 26is similarly attached to a magnetic pole section 21 b formed in aposition opposing to the magnetic pole 21 a across the stator 1, and ametal wire 27 is multiple-wound on this winding drum 26.

On the tip end surface of the magnetic pole section 21 a facing themovable section 1 there are fixed permanent magnets 24 and 25 arrangedin the axial direction of the shaft 11. Also on the tip end surface ofthe magnetic pole section 21 b facing the movable section 1 there arefixed permanent magnets 24 and 25 arranged in the axial direction of theshaft 11. These permanent magnets 24 ad 25 are formed with tile shapedrare-earth magnets or the like having the same axis, diameter, andlength, and are arranged adjacent to each other in the axial direction.Here, these permanent magnets 24 and 25 have radial anisotropy in whichthe magnetic poles are arranged orthogonal to the axial direction, andthe arrangement of the magnetic poles is such that they are mutuallyopposite. Specifically, as for the permanent magnet 24, the N polethereof is arranged on the outer diameter side and the S pole thereof isarranged on the inner diameter side, and as for the other permanentmagnet 25, the N pole thereof is arranged on the inner diameter side andthe S pole thereof is arranged on the outer diameter side.

The two plate springs 3 are distanced from each other in the axialdirection of the shaft 11, and are arranged so as to have the yoke 21therebetween. These two plate springs 3 are of the same shapepunch-formed from a metal plate having a uniform thickness, and areformed in a “number 8” shape when seen from the axial direction of theshaft 11. In the location corresponding to the center portion where thelines of the “number 8” shape intersect with each other, there isrespectively formed a through hole 3 a that supports the tip end or rearend of the shaft 11. Moreover, in the locations corresponding to areasinside the round portions of the “number 8” shape, there arerespectively formed through holes 3 b and 3 c that sufficiently allowthe above mentioned coil 22 or 23 to be inserted therethrough.Furthermore, in the locations corresponding to the top most portion andbottom most portion of the “number 8” shape, there are respectivelyformed small holes 3 d and 3 e for fixing the plate springs 3 to theyoke 21.

Each of the plate springs 3 supports the shaft 11 in a position partwayalong the axial direction of the coil 22. To describe in further detail,one of the plate springs 3 that supports the tip end of the shaft 11 isfixed with the tip end side of the shaft 11 inserted through the throughhole 3 a, and is fixed to the yoke 21 in a position further from thecenter of the shaft 11 than the coil 22 or 23, with a screw passingthrough the small hole 3 d and a screw passing through the small hole 3e. Moreover, the other plate spring 3 that supports the rear end of theshaft 11 is fixed with the rear end side of the shaft 11 insertedthrough the through hole 3 a, and is fixed to the yoke 21 in a positionfurther from the center of the shaft 11 than the coil 22 or 23, withscrews passing through the small holes 3 d and 3 e.

The one plate spring 3 is such that the coil 22 projects from thethrough hole 3 b towards the tip end side of the shaft 11 and the coil23 projects from the through hole 3 c towards the tip end side of theshaft 11, and the other plate spring 3 is such that the coil 22 projectsfrom the through hole 3 b towards the rear end side of the shaft 11 andthe coil 23 similarly projects from the through hole 3 c towards therear end side of the shaft 11. The gap between these two plate springs 3along the axial direction of the shaft 11 is narrower than the dimensionof the coil 22 or 23, and the through holes 3 b and 3 c serve as“clearances” to avoid interference with the coil 23.

Rather than slidably and reciprocatably supporting the movable elementas conventionally practiced, each of the plate springs 3 supports themovable section 1 in two positions on the tip end side and the rear endside of the shaft 11, and they elastically deforms themselves to therebysupport the movable section 1 while allowing it to reciprocate in theaxial direction of the shaft 11. Pre-adjustments such as increasing thedistance between the through hole 3 a for supporting the shaft 11 andthe small hole 3 d or 3 e (the length of the plate spring itself, notthe direct distance) to the possible maximum length, or reducing theplate thickness, are performed, so that the amount of deformation ineach of the plate springs 3 when the movable section 1 reciprocates,becomes smaller than the amount of deformation that leads to apossibility of breakage due to the fatigue caused by repetitive forcedelastic deformation thereof. However, when the entire linear actuator isseen from the axial direction of the shaft 11, the outer shape of eachof the plate springs 3 is in a size that does not allow it to stick outfrom the outer shape of the yoke 21.

The behavior of an operation of the linear actuator configured in thisway is described below. If an alternating current (sinusoidal current,square-wave current) is applied to the coils 22 and 23 in a state wherea current flows through the coils 22 and 23 in a predetermineddirection, a magnetic flux is guided, in the permanent magnet 24, fromthe south pole to the north pole, and a magnetic flux loop thatcirculates through an outer circumference section of the yoke 21, themagnetic pole section 21 a, the permanent magnet 24, the movable element12, the shaft 11, and the outer circumference section of the yoke 21, inthis order is thereby formed. As a result, a force acts on the movablesection 1 in the axial direction from the rear end to the tip end of theshaft 11, and the movable section 1 is pushed by this force and moved inthe same direction. On the other hand, in a state where a current flowsthrough the coils 22 and 23 in a direction opposite to the abovementioned predetermined direction, a magnetic flux is guided, in thepermanent magnet 25, from the south pole to the north pole, and amagnetic flux loop that circulates through the outer circumferencesection of the yoke 21, the magnetic pole section 21 a, the permanentmagnet 25, the movable element 12, the shaft 11, and the outercircumference section of the yoke 21, in this order is thereby formed.As a result, a force acts on the movable section 1 in the axialdirection from the tip end to the rear end of the shaft 11, and themovable section 1 is pushed by this force and moved in the samedirection. The flow directions of the currents flowing into the coils 22and 23 are alternately changed by the alternating current, and themovable section 1 thereby repeats the above operation and reciprocatesin the axial direction of the shaft 11 with respect to the stator 2.

In the above linear actuator, rather than slidably and reciprocatablysupporting the movable section, each of the plate springs 3 supports themovable section 1 in two positions on the tip end side and the rear endside of the shaft 11, and they elastically deforms themselves to therebysupport the movable section 1 while allowing it to reciprocate in theaxial direction of the shaft 11. As a result, no wear or slidingresistance occurs on the movable section 1. Therefore, even after usefor a long period of time, the precision of the bearing support does notdecrease, and a high level of reliability can be attained. Furthermore,there is no power consumption loss caused by sliding resistance, and animprovement in the performance can be achieved. Moreover, in the abovelinear actuator, each of the plate springs 3 avoids interference withthe coils 22 and 23 and is supported by the stator 2 in a position thatis away from the coils 22 and 23 with the movable element as a basepoint. As a result, it becomes possible to arrange the voluminous coils22 and 23 and the two plate springs 3 in close proximity to each other.Therefore, a reduction in the size of the linear actuator can berealized.

Next, a modified example of the damping apparatus shown in FIG. 1 isdescribed, with reference to FIG. 2. The apparatus shown in FIG. 2differs from the apparatus shown in FIG. 1 in that instead of having therelative velocity sensor 33, there is provided a current detector 51that detects a driving current, and stabilization is realized based onthe current detected by the current detector 51. A stabilizingcontroller 61 estimates an induced voltage generated by the linearactuator 31 according to a coil current (driving current) of the linearactuator 31, a voltage command or a terminal voltage output from a powercircuit 71, or the like, and based on this, it estimates a relativevelocity between the linear actuator 31 and the auxiliary mass 32. Thisestimation value is fed back and a damping force is thereby generated inthe linear actuator 31. As a result, the influence of disturbancevibrations can be reduced.

For the terminal voltage, a signal found by multiplying a voltagecommand by a voltage amplifier gain may be used in a voltage amplifierincluded in the power circuit 71.

FIGS. 6 (a) and (b) are diagrams showing a gain characteristic and aphase characteristic as examples of responses of the linear actuator(induced voltage feed back absent) having a spring element forsupporting the auxiliary mass, with respect to a command signal. FIGS. 7(a) and (b) are diagrams showing a gain characteristic and a phasecharacteristic as examples of a response of the linear actuator withrespect to a command signal (induced voltage feed back present, orrelative velocity feed back present).

In the case where induced voltage feed back is absent, then with respectto changes in the resonance frequency of the actuator, changes in thegain characteristic shown in FIG. 6 (a) and the phase characteristicshown in FIG. 6 (b) are steep. On the other hand, it can be seen that inthe damping apparatus for an automobile according to the presentembodiment, by performing induced voltage feed back (feed back controlwith use of velocity information), the gain characteristic shown in FIG.7 (a) and the phase characteristic shown in FIG. 7 (b) are moderate evenif the resonance frequency of the actuator changes, and thereforechanges in the response with respect to the command signal becomesmaller and an influence on control performance becomes smaller.

Moreover, by performing a feed back control with use of velocityinformation obtained by calculation, the resonance characteristic of theactuator becomes moderate. Therefore, even if the resonance frequency ofthe actuator changes, the gain characteristic and the phasecharacteristic are moderate, and hence changes in response with respectto the command signals are small, and influence on the controlperformance can be reduced.

Second Embodiment

Next, a configuration of a damping apparatus according to a secondembodiment of the present invention is described. FIG. 3 is a blockdiagram showing a configuration of the damping apparatus according tothe second embodiment. In FIG. 3, the damping apparatus is connected toan automobile body frame (main system mass) 41 serving as a controlobject, and controls (damps) vibrations in the vertical direction(gravitational direction) that occur in the body frame (main systemmass) 41.

The damping apparatus in the present embodiment is a so-called activedynamic vibration absorber, and includes a current detector 63 thatdetects driving current to a linear actuator 31, a terminal voltagedetector 64 that detects terminal voltage of the linear actuator 31, andthe linear actuator 31 that drives based on detection results of thecurrent detector 63 and the terminal voltage detector 64. The dampingapparatus uses the driving force of the linear actuator 31 to drive theauxiliary mass 32 in the vertical direction (the direction of vibrationsto be damped), and applies to the main system mass 41 an inertial forceof the auxiliary mass including the auxiliary mass 32 as a reactionforce, thereby suppressing vibrations of the main system mass 41.

The current detector 63 shown in FIG. 3 detects the current supplied tothe linear actuator 31 and supplies this to a controller 62. Moreover,the terminal voltage detector 64 detects the terminal voltage applied tothe linear actuator 31, and supplies this to the controller 62. In thecase where the linear actuator 31 is driven, the linear actuator 31generates an induced electromotive force proportional to velocity. Bycalculating this induced electromotive force, a velocity signal can beobtained. Moreover, it is possible to obtain a vibration displacementsignal by integration processing it, and to obtain vibrationacceleration by differentiation processing it.

For example, as shown in FIG. 4 and FIG. 5, a terminal voltage V and acurrent i are detected, and are output as an induced voltage E throughan amplifying circuit and a differentiating circuit. In this case, gainsK1 and K2 corresponding to a wire wound resistance R and a wire woundinductance L need to be set. This setting is adjusted by applying acurrent of a predetermined frequency while the movable section of thelinear actuator (movable element, auxiliary mass) is in a state of beingrestrained so that the output becomes zero. Since the relationshipE=V−R·i−L(di/dt) holds for the induced voltage E, it is possible to findthe induced voltage E by detecting the terminal voltage V and thecurrent i.

In the case where a spring constant close to an optimum value for thedynamic vibration absorber can be obtained by means of the magneticspring characteristic or mechanical spring element, then by adjustingthe damping force that the linear actuator 31 generates, a high level ofdamping effect can be achieved without supplying energy for damping. Thedamping force can be adjusted by connecting a load resistance to bothends of the coil of the linear actuator 31 and by changing the level ofthis load resistance.

The controller 62, based on the induced voltage calculated from thecurrent and terminal voltage detected by the current detector 63 and theterminal voltage detector 64, calculates the relative velocity, relativedisplacement, or relative acceleration of the linear actuator 31, andderives an optimum driving amount (control amount) of the linearactuator 31 for the damping apparatus to obtain an optimum springcharacteristic and damping characteristic for vibration-damping the mainsystem mass 41, and the derived result is output to a power amplifier 72as a command signal. Electric power is supplied from a power supplycircuit 90 to the power amplifier 72. The power amplifier 72, accordingto the command signal of the controller 62, drives the linear actuator31, and the linear actuator 31 drives (vibrates) the auxiliary mass 32in the vertical (gravitational) direction to thereby damp the mainsystem mass 41.

According to the above embodiment, without use of a sensor for detectingthe relative displacement, relative velocity, and relative accelerationbetween the movable section and the fixation section of the actuator,the relative velocity, relative displacement, or relative accelerationof the linear actuator 31 are calculated based on the induced voltagecalculated from the current and the terminal voltage of the linearactuator 31, and the linear actuator 31 is controlled based on therelative velocity, relative displacement, or relative acceleration. As aresult, a high level of reliability can be ensured.

Moreover, by making use of displacement information obtained bycalculation, a spring effect can be obtained. Furthermore, by making useof velocity information obtained by calculation, a damping effect can beobtained.

The terminal voltage may be found from a command value of the voltage tobe applied to the actuator.

Next, a modified example of the method of detecting inducedelectromotive force shown in FIG. 5 is described, with reference to FIG.8. The method of detecting induced electromotive force shown in FIG. 8differs from the method of detecting induced electromotive force shownin FIG. 5 in that in order to limit the control bandwidth forsuppressing resonance with the feed back of an estimated velocity valueto be in the vicinity of the resonance frequency of the linear actuator31, there is provided a band-pass filter (BPF). This band-pass filter isa filter for obtaining a damping effect only within the vicinity of theresonance frequency of the linear actuator 31 (frequency close to thenatural frequency), and the phase of this band-pass filter is set sothat it becomes 0° in the vicinity of the resonance frequency of theactuator.

By providing the band-pass filter, the noise component of direct currentcan be suppressed and it is possible to adjust the phase. Therefore, thecertainty of an estimated induced voltage can be improved.

Next, a modified example of the method of detecting inducedelectromotive force shown in FIG. 8 is described, with reference to FIG.9. The method of detecting induced electromotive force shown in FIG. 7differs from the method of detecting induced electromotive force shownin FIG. 8 in that in order to suppress the high frequency noisecomponent, there are provided two low pass filters (LPF). The cutofffrequency of these low pass filters is set to a frequency higher thanthe resonance frequency (natural frequency) of the linear actuator 31.

By providing the low pass filters, the high frequency noise componentcan be removed, and therefore generation of an abnormal noise caused bythe noise component can be suppressed.

The damping apparatus for an automobile according to the presentinvention is effective if attached to the automobile component such asthe body frame of the automobile, components in the vicinity of theengine mount or radiator, or to components under a rear luggage carryingsection or trunk.

Moreover, the linear actuator 31 is an actuator that useselectromagnetic force, and is effective if it uses a reciprocating motorfor example.

As described above, in the actuator in which the movable section issupported with a spring element, even if an external excitation forcedue to the uneven road surface acts on the actuator while the automobileis traveling, it is possible to suppress generation of excessivedisplacement caused by the external excitation force or resonancephenomena. Therefore, it is possible to prevent generation of anabnormal noise caused, for example, by the movable section of theactuator colliding with a stopper. Moreover, since it is possible todetect resonance phenomena on the driving circuit side, there is no needto provide a sensor or the like in the actuator main unit, and theactuator main unit can be miniaturized. Furthermore, even in the casewhere an error occurs in the coil constant due to individual differencesor age related changes in the actuator, it is possible to preventgeneration of a direct current component of unwanted current in thedamping control. Moreover, since the high frequency noise component isnot to be amplified, it is possible to reduce the generation level ofundesired sound or abnormal noises. Furthermore, since the band-passfilter and low pass filter are provided in the vibration velocity feedback, and are made independent from a current feed back circuit, it ispossible to prevent their influence on the response of the actuator withrespect to high frequency driving commands.

Third Embodiment

Next, a configuration of a damping apparatus according to a thirdembodiment of the present invention is described, with reference to thedrawing. FIG. 10 is a block diagram showing a configuration of the sameembodiment. Here, the present embodiment is described on the assumptionthat an engine that performs cylinder number control is an excitationsource in an automobile. In this diagram, reference symbol 41 denotes anautomobile body frame. Reference symbol 40 denotes an engine capable ofperforming cylinder number control according to the operation statethereof, and this engine 40 is a vibration generating source (excitationsource). Reference symbol 44 denotes a seat of a driver's seat(hereunder, simply referred to as seat), and this seat 44 is a point atwhich vibrations are measured. Reference symbol 43 denotes anacceleration sensor attached to the seat 44, and this detects theacceleration of the seat 44. Reference symbol 31 denotes a linearactuator (reciprocating motor) attached to the automobile body frame 41,and this suppresses vibrations by vibrating an auxiliary mass 32 fordamping vibrations generated by the engine 40. Reference symbol 52denotes a control section that controls driving of the linear actuator31 based on the vibrations generated by the excitation source and thevibrations detected at the measuring point.

Reference symbol 510 denotes a pulse IF (interface) that receives theinput of an ignition pulse to be given to the engine 40. Referencesymbol 520 denotes a sensor IF (interface) to which is input an outputof the acceleration sensor 43. Reference symbol 530 denotes a frequencydetection section that detects the frequency of the inputted ignitionpulse. Reference symbol 540 denotes a FFT section that executes FFT(Fast Fourier Transform). It extracts which frequency component and towhat extent is it included in an output signal from the accelerationsensor 43, and outputs a phase/amplitude FB (feed back) signal of aprimary vibration mode and a phase/amplitude FB signal of a secondaryvibration mode. Reference symbol 550 denotes a primary command ROM thatpre-stores a command value for generating vibrations for the primaryvibration mode, and reads and outputs the command value according to thefrequency detected in the frequency detection section 530. Referencesymbol 560 denotes a secondary command ROM that pre-stores a commandvalue for generating vibrations for the secondary vibration mode, andreads and outputs the command value according to the frequency detectedin the frequency detection section 530.

Reference symbol 570 denotes a primary frequency calculation section towhich is input a primary vibration command value read from the primarycommand ROM 550, and a primary vibration amplitude FB value and aprimary vibration phase FB value output from the FET section 540, and itcalculates and outputs a primary vibration command value and primaryphase command value of the vibration to be excited. Reference symbol 580denotes a sine wave transmitter to which is input the primary vibrationcommand value and the primary phase command value output from theprimary frequency calculation section 570, and a vibration frequencyvalue output from the frequency detection section 530, and that outputsa primary current command value. Reference symbol 590 denotes asecondary frequency calculation section to which is inputs a secondaryvibration command value read from the secondary command ROM 560, and asecondary vibration amplitude FB value and a secondary vibration phaseFB value output from the FET section 540, and it calculates and outputsa secondary vibration command value and secondary phase command value ofthe vibration to be excited. Reference symbol 600 denotes a sine wavetransmitter to which is input the secondary vibration command value andthe secondary phase command value output from the secondary frequencycalculation section 590, and a vibration frequency value output from thefrequency detection section 530, and that outputs a secondary currentcommand value. Reference symbol 610 denotes a zero command outputsection that outputs a zero current command value. Reference symbol 53denotes a current amplifier that outputs a motor current that flowsthough the linear actuator 31, based on a superimposed current commandvalue in which the zero current command value, the primary currentcommand value, and the secondary current command value are superimposed.

Next, with reference to FIG. 10, there is described an operation forsuppressing only vibrations that should be suppressed among thevibrations that occur in the automobile body frame 41, while generatingvibrations to be applied superimposably. In an automobile equipped witha six-cylinder engine, when a cylinder stop control from six cylindersto three cylinders is performed, the primary frequency calculationsection 570 calculates and outputs a command value for suppressingvibrations that newly occur because of the switch to three cylinderdriving (vibrations that occur in three cylinder driving operation). Onthe other hand, the secondary frequency calculation section 590calculates and outputs a command value for newly generating vibrationsthat have stopped occurring due to the switch to the three cylinderdriving operation (vibrations generated in six cylinder drivingoperation). When a superimposed current command value, in which thecommand value for suppressing vibrations that occur in the threecylinder driving operation and the command value for newly generatingvibrations to be generated in the six cylinder driving operation aresuperimposed, is output to the current amplifier 53, the auxiliary mass32 vibrates in the linear actuator 31 so as to suppress unwantedvibrations, and to generate vibrations to be newly generated. As aresult, even if a cylinder stop control is performed from six cylindersto three cylinders, vibrations of the six cylinder driving operationcontinue to be generated, so that there is no discomfort to the driver.

Fourth Embodiment

Next, with reference to FIG. 11, a fourth embodiment is described. Thedamping apparatus shown in FIG. 11 differs from the damping apparatusshown in FIG. 10 in that there is provided a plurality of measuringpoints for detecting vibrations, and there is provided a plurality oflinear actuators for performing excitation. A control section 52, atmeasuring points 441, 442, 443, and 44 n, finds command values for thevibrations to be suppressed and for the vibrations to be generated, andoutputs these to the respective linear actuators 31, 301, 302, and 30 n.Thus, vibrations that need to be suppressed can be reduced andvibrations that need to be emphasized can be increased. Therefore, forexample, it becomes possible to perform a control such that enginevibrations are suppressed while increasing bass sound vibrationsgenerated from audio speakers when playing music, based on audio signalsof music being played. Moreover, by suppressing engine vibrations, itbecomes possible to reduce muffleness of sound within the interior ofthe automobile.

Thus, in order to suppress unwanted vibrations while generatingpredetermined vibrations as necessary, in the damping apparatusincluding a means for exciting the automobile body frame 41 by vibratingthe auxiliary mass 32 supported by the linear actuator 31, the frequencyof the engine 40 that vibrates the automobile body frame 41 and thevibrations at the seat 44 are detected, and command values forvibrations to be suppressed and for vibrations to be generated are foundbased on the frequency of the engine 40 and the vibrations at the seat44, and a control signal in which these command values are superimposed,is output to the linear actuator 31. As a result, it is possible tosuppress unwanted vibrations and to generate predetermined vibrations asnecessary, and to prevent discomfort due to the vibration control frombeing given to the driver.

Fifth Embodiment

Next, a configuration of a damping apparatus according to a fifthembodiment of the present invention is described, with reference to thedrawing. FIG. 12 is a block diagram showing a configuration of the sameembodiment. In this diagram, reference symbol 41 denotes an automobilebody frame on which an engine such as internal combustion engine ismounted, and a vibrating system of the automobile body is formed due torotation drive of the engine. Reference symbol 30 denotes an excitationsection 30 that vibrates an auxiliary mass with a linear actuator tothereby damp vibrations generated in the body of the automobile bodyframe 41. For this excitation section 30, it is possible to use a linearactuator such as voice coil motor or a reciprocating motor. Referencesymbol 70 denotes a power circuit that drives the excitation section 30.Reference symbol 604 denotes a mapping control section that makesreference to internal mapping data and performs damping control.Reference symbol 605 denotes a frequency domain adaptive filter sectionthat performs damping control with a frequency domain adaptive filter.Reference symbol 606 denotes a time domain adaptive filter section thatperforms damping control with a time domain adaptive filter.

The frequency domain adaptive filter section 605 and the time domainadaptive filter section 606 update map data held in the mapping controlsection 604, based on results from the adaptive filters. Referencesymbol 607 denotes a control switching section that selects any one ofthe mapping control section 604, the frequency domain adaptive filtersection 605, and the time domain adaptive filter section 606 to performdamping control, and it switches controls to be used based on, anacceleration at a measuring point in a predetermined position of theautomobile body frame 41, an acceleration reference value, and a changerate of engine revolution speed. Moreover, the frequency domain adaptivefilter section 605 transfers a transfer function G′ (s) to the timedomain adaptive filter section 606 and updates it. The inverse number of(S(n)−S(n−1)/(M(n)−M(n−1)) calculated in the frequency domain adaptivefilter section 605 corresponds to G′(s). Reference symbol 608 denotes anacceleration reference value table in which acceleration referencevalues corresponding to revolution speed are stored for each of theoperating states. Reference symbol 609 denotes a revolution speed changerate measuring section that measures the change rate in enginerevolution speed based on engine pulse signals, and calculates enginerevolution speed N and revolution speed change rate dN/dt and updatesthem for each engine pulse signal, based on the time intervals of enginepulse signals being generated. The automobile body frame 41 includes anacceleration sensor that detects an acceleration A at the measuringpoint and outputs a measuring point acceleration signal, and a function(not shown in the drawing) for outputting an operating state signal D0that shows an operating state at the present moment (gear position, airconditioner ON/OFF, accelerator opening, and so forth).

Here, with reference to FIG. 14 to FIG. 16, an operation of each controlsection is described. Control operations shown in FIG. 14 to FIG. 16 areessentially controls according to conventional techniques, and thedetailed descriptions thereof are therefore omitted.

FIG. 14 is a diagram showing an operation of the mapping control section604 shown in FIG. 12. The mapping control section 604 selects a controlsignal data map based on an operating state signal and an enginerevolution speed found from the engine pulse signals, reads an amplitudecommand value and phase command value predefined in this data map, andoutputs this read amplitude command value and phase command value to thepower circuit 70. The power circuit 70, based on these command values,controls vibrations of the excitation section to thereby reducevibrations of a damping target (automobile body).

FIG. 15 is a diagram showing an operation of the time domain adaptivefilter section 606 shown in FIG. 12. The time domain adaptive filtersection 606 receives the input of the measuring point accelerationsignal and the engine pulse signal, finds sine wave exciting forcecommand values (amplitude command value and phase command value) basedon the estimated transfer function G (s) of the signal transfercharacteristic, and outputs these sine wave exciting force command valueto the power circuit 70. The power circuit 70, based on these commandvalues, controls vibrations of the excitation section to thereby reducevibrations of a damping target (automobile body).

FIG. 16 is a diagram showing an operation of the frequency domainadaptive filter section 605 shown in FIG. 12. The frequency domainadaptive filter section 605 receives the input of a measuring pointacceleration signal and engine pulse signal, finds a force command valueof the force to be generated based on the frequency component of thedamping target obtained with use of Fourier transform, finds sine waveexciting force command values (amplitude command value and phase commandvalue) obtained based on this force command, and outputs these sine waveexciting force command values to the power circuit 70. The power circuit70, based on these command values, controls vibrations of the excitationsection to thereby reduce vibrations of a damping target (automobilebody).

Next, an operation of the damping apparatus shown in FIG. 12 isdescribed. First, when the engine of an automobile is started, thecontrol switching section 607 selects the mapping control section 604.Thus, mapping control is performed. In this state, the control switchingsection 607 compares an acceleration signal at the measuring point onthe automobile body frame 41 with an acceleration reference value storedin the acceleration reference value table 608, and if the detectedacceleration exceeds the acceleration reference value, it performsswitching from the mapping control to an adaptive filter. In the casewhere switching is made from the mapping control to the adaptive filter,the control switching section 607 makes reference to the output of therevolution speed change rate measuring section 609, and it switches tothe time domain adaptive filter section 606 if the change rate issignificant and switches to the frequency domain adaptive filter section605 if the change rate is small. Moreover, when the frequency domainadaptive filter section 605 is being operated, during the course of anadaptive filter calculation, the estimated transfer function of thesignal transfer characteristic ((S(n)−S(n−1))/(M(n)−M(n−1)) that isessential in the time domain adaptive filter section 606 is found. Thisestimated transfer function corresponds to 1/G′ (s), and therefore theestimated transfer function G′ (s) of the time domain adaptive filter 6is updated based on this result.

Having shifted to the adaptive filter, the control switching section 607performs switching from the adaptive filter back to the mapping controlat the point in time when acceleration is below the accelerationreference value. At this time, in the frequency domain adaptive filtersection 605 or the time domain adaptive filter section 606, sine waveexciting force commands that enable effective damping are found by meansof the operation of the adaptive filter. Therefore the frequency domainadaptive filter section 605 or the time domain adaptive filter section606, based on the found excitation force command value, updates themapping data held in the mapping control section 604. With thisoperation, the mapping data is updated to the optimum mapping data atthe present moment. Therefore, it is possible to prevent the dampingperformance from being degraded due to the influence of individualdifferences or age related changes, while maintaining appropriateexecution of the damping control process.

Next, with reference to FIG. 13, timings at which the control switchingsection 607 switches the respective controls are described. FIG. 13 is adiagram showing operations for switching control types based on statevalues. In FIG. 13, based on the engine revolution speed N and theoperating state value D0, the reference values obtained upon referenceto the acceleration reference value table 608 are shown as A1 (N, D0) orA2 (N, D0). A1 (N, D0) is a reference value for shifting from themapping control to the adaptive filter, and A2 (N, D0) is a referencevalue for shifting from the adaptive filter to the mapping control,where a relationship A2 (N, D0)≦A1 (N, D0) is satisfied. Moreover,reference values for performing shifting between adaptive filter typesare shown as W1 to W4. W1 is a reference value for shifting from thefrequency domain adaptive filter to the time domain adaptive filter,based on engine revolution speed change rate dN/dt. W2 is a referencevalue for shifting from the time domain adaptive filter to no control,based on engine revolution speed change rate dN/dt. W3 is a referencevalue for shifting from the time domain adaptive filter to the frequencydomain adaptive filter, based on engine revolution speed change ratedN/dt. W4 is a reference value for shifting from no control to the timedomain adaptive filter, based on engine revolution speed change ratedN/dt. Reference values W1 to W4 satisfy relationships W1<W2, W3<W4,W1≧W3, and W2≧W4. Moreover, the mapping control state (initial state) isshown as C0=1, the control state with the frequency domain adaptivefilter is shown as C0=2, the control state with the time domain adaptivefilter is shown as C0=3, and the state without adaptive filter controlis shown as C0=4. As shown in FIG. 13, by selecting and executing acontrol type optimum at the present moment based on the reference valuesA1, A2 found from the engine revolution speed N and the revolution speedchange rate dN/dt and the reference values W1 to W4 for adaptive filterswitching, an optimum damping control becomes possible.

Reference values A1 and A2 may be the same value. However, these valuesmay be set such that A2<A1 is satisfied, and after the accelerationreference value has been exceeded and a shift to adaptive filter controlhas been made, a hysteresis is provided when returning to the mappingcontrol, so that the control returns to the mapping control ifacceleration is below the acceleration reference value by the hysteresiswidth. Thus, the damping performance can be further improved, and themapping data can be updated to have higher quality. Moreover, whenreturning to the mapping control, the control may return to the mappingcontrol in the case where acceleration is below the accelerationreference value while revolution speed change rate is above thepredetermined value. Thus, the control stays in the adaptive filtercontrol as long as possible, and the mapping data can be updated whilethe damping performance is enhanced.

Moreover, when updating the mapping data, only the engine revolutionspeed data for when the control has shifted from the mapping control tothe adaptive filter control may be updated, and all of the revolutionspeed data while acceleration is below the acceleration reference valueduring the performance of the adaptive filter control may be updated.Furthermore, the timing of updating the mapping data is such that themapping data is updated when the control returns to the mapping control,and in addition, the mapping data may be updated every time accelerationis below the acceleration reference value by a predetermined value whileperforming the adaptive filter control. Moreover, the timing of updatingthe transfer function is such that the transfer function is updated atconstant time intervals, and in addition, it may be updated every timethe revolution speed becomes a revolution speed away from a previouslyupdated revolution speed by a predetermined interval. Moreover, in thecase where the revolution speed change rate during the performance ofthe adaptive filter control is too significant, the operation of theadaptive filter may be stopped (no control) in order to avoid itsadverse influence.

As described above, in the case where the damping performance with themapping control is degraded due to individual differences and agerelated changes, the control is switched to the adaptive filter tothereby improve the damping performance and update the mapping data ofthe mapping control. Therefore, it is possible to recover the dampingperformance with the mapping control. Moreover, when performing theadaptive filter, it is switched to any one of the frequency domain, timedomain, and no control, according to the revolution speed change rateand response. Therefore, when the revolution speed changes, it ispossible to prevent vibrations from being made adversely significant bythe adaptive filter. Furthermore, since the transfer function requiredin the time domain adaptive filter is updated with the calculationprocess of the frequency domain adaptive filter, it is possible toprevent the characteristic of the time domain adaptive filter from beingdegraded due to the changes in the transfer function.

Sixth Embodiment

Next, a damping apparatus according to a sixth embodiment of the presentinvention is described, with reference to the drawing. FIG. 17 is ablock diagram showing a configuration of the damping apparatus accordingto the same embodiment. In FIG. 17, reference symbol 30 denotes anexcitation section that vibrates an auxiliary mass (weight) and uses thereaction force thereof to thereby suppress vibrations of a dampingtarget device such as an automobile. Reference symbol 41 denotes anautomobile body frame to which the excitation section 30 is attached.The excitation section 30 controls (damps) vibrations in the verticaldirection (gravitational direction) that occur in the automobile bodyframe (main system mass) 41. Reference symbol 72 denotes a poweramplifier that supplies current for driving a linear actuator providedwithin the excitation section 30. Reference symbol 65 denotes a currentcontrol section that controls current to be supplied to the linearactuator, according to the force to be generated in the excitationsection 30. Reference symbol 631 denotes a current detection sectionthat detects current being supplied to the excitation section 30.Reference symbol 641 denotes an application voltage detection sectionthat detects voltage being supplied to the power amplifier 72. Referencesymbol 66 denotes an actuator vibration velocity estimation sectionthat, based on the output (current value and voltage value) from thecurrent detection section 631 and the application voltage detectionsection 641, estimates the vibration velocity of the linear actuatorprovided within the excitation section 30. Reference symbol 67 denotesan ideal actuator inverse characteristic section that receives the inputof a vibration velocity value output from the actuator vibrationvelocity estimation section 66 and outputs a force command signal thatan ideal actuator should output based on the ideal actuator inversecharacteristic. Reference symbol 68 denotes a predetermined value outputsection that outputs a force command value of a predetermined value.

Here, with reference to FIG. 19, the detailed configuration of theexcitation section 30 shown in FIG. 17 is described. FIG. 19 is adiagram showing the detailed configuration of the excitation section 30shown in FIG. 17. In this diagram, reference symbol 32 denotes anauxiliary mass (weight) to be attached to the automobile body frame 41.Reference symbol 34 denotes stators that constitute a linear actuator(reciprocating motor), and these stators 34 are fixed to the automobilebody frame 41. Reference symbol 12 denotes a movable element thatconstitutes the linear actuator (reciprocating motor), and this movableelement reciprocates, for example, in the gravitational direction (inthe vertical direction in FIG. 3). The excitation section 30 is fixed onthe automobile body frame 41 so that the direction of the vibrations ofthe automobile body frame 41 to be suppressed matches the direction ofthe reciprocation (thrust direction) of the movable element 12.Reference symbol 3 denotes a plate spring that supports the movableelement 12 and the auxiliary mass 32 while allowing them to move alongthe thrust direction. Reference symbol 11 denotes a shaft that joins themovable element 12 to the auxiliary mass 32, and is supported by theplate spring 3. Reference symbol 35 denotes stoppers that limit themovable range of the movable element 12, and limit the movable range onboth ends of the movable element 12 (upper limit and lower limit in FIG.19). This excitation section 30 constitutes a dynamic vibrationabsorber.

Next, an operation of the excitation section 30 shown in FIG. 19 isdescribed. In the case where an alternating current (sinusoidal current,square-wave current) is applied to a coil (not shown in the drawing)that constitutes the linear actuator (reciprocating motor), in a statewhere a current in a predetermined direction flows through the coil,magnetic flux is, in the permanent magnet, guided from the south pole tothe north pole, forming a magnetic flux loop. As a result, the movableelement 12 moves in the direction opposite to that of gravity (upwarddirection). On the other hand, if a current in the direction opposite tothat of the predetermined direction flows through the coil, then themovable element 12 moves in the gravitational direction (downwarddirection). The direction of the current flow into the coils isalternately changed by the alternating current, and the movable element12 thereby repeats the above operation and reciprocates in the axialdirection of the shaft 11 with respect to the stator 34. Thus, theauxiliary mass 32 joined to the shaft 11 vibrates in the verticaldirection. By controlling the acceleration of the auxiliary mass 32based on control signals output from the current control section 65, thecontrol force is adjusted and vibrations of the automobile body frame 41can be reduced.

Next, an operation of the damping apparatus shown in FIG. 17 isdescribed, with reference to FIG. 17. First, the current detectionsection 631 detects the current supplied to the excitation section 30,and supplies this to the current control section 65 and the actuatorvibration velocity estimation section 66. Moreover, the applicationvoltage detection section 641 detects the voltage applied to theexcitation section 30, and supplies this to the actuator vibrationvelocity estimation section 66. In the case where the linear actuator inthe excitation section 30 is driven, the linear actuator generates aninduced electromotive force proportional to velocity. By calculatingthis induced electromotive force, the actuator vibration velocityestimation section 66 can obtain a vibration velocity signal.

For example, an application voltage V and a current i are detected, andare output as induced voltage E through an amplifying circuit anddifferentiating circuit. In this case, gains K1 and K2 corresponding toa wire wound resistance R and a wire wound inductance L need to be set.This setting is adjusted by applying a current of a predeterminedfrequency while the movable section of the linear actuator (movableelement, auxiliary mass) is in a state of being restrained so that theoutput becomes zero. Since the relationship E=V−R·i−L(di/dt) holds forthe induced voltage E, it is possible to find the induced voltage E bydetecting the terminal voltage V and the current i. Moreover, in thecase where a spring constant close to an optimum value in the excitationsection 30 can be obtained by means of the magnetic springcharacteristic or mechanical spring element, then by adjusting thedamping force that the linear actuator generates, a high level ofdamping effect can be achieved without supplying energy for damping. Thedamping force can be adjusted by connecting a load resistance to bothends of the coil of a linear actuator 11A and by changing the level ofthis load resistance.

The actual actuator output for a command value at the present moment isreflected on the output from the actuator vibration velocity estimationsection 66. On the assumption that the linear actuator is an idealactuator, the current control section 65 receives the input of a commandsignal of a force required when the ideal actuator outputs a vibrationvelocity estimated by the actuator vibration velocity estimation section66. Therefore, the ideal actuator inverse characteristic section 67outputs a command signal of a force required when the ideal actuatoroutputs the vibration velocity estimated by the actuator vibrationvelocity estimation section 66. Expression (1) shows an example of thetransfer function of the ideal actuator inverse characteristic.

Gi(s)=(Mis2+Cis+Ki)/s  (1)

where Mi: auxiliary mass (ideal value), Ci: damping coefficient (idealvalue), Ki: spring constant (ideal value), and the damping coefficientof the transfer function falls within a range of 1/100 to 100 times acritical damping (damping attenuation factor=1).

The difference value between the actual command signal and the output ofthe ideal actuator inverse characteristic section 67 is fed back as acorrection value of the command signal, and thereby the actual actuatorcan behave as the ideal actuator. The current control section 65, basedon the current detected by the current detection section 631 and thecommand signal output from the ideal actuator inverse characteristicsection 67, derives an optimum driving amount (control amount) of thelinear actuator so that the optimum spring characteristic and dampingcharacteristic for the excitation section 30 to damp the vibration ofthe automobile body frame 41 can be obtained, and outputs the derivedresult as a command signal to the power amplifier 72. The poweramplifier 72, according to the command signal of the current controlsection 65, drives the excitation section 30 so that the auxiliary mass32 vibrates in the vertical (gravitational) direction. With the reactionforce caused by the vibration of this auxiliary mass 32, the vibrationsoccurring in the automobile body frame 41 are suppressed.

There may be provided a band-pass filter that limits the ideal actuatorinverse characteristic to a band in the vicinity of a resonancefrequency of the actuator.

Thus, by making the ideal actuator characteristic equal to that of anoptimum dynamic vibration absorber, it becomes possible for an activedynamic vibration absorber to behave as the optimum dynamic vibrationabsorber. Therefore, in the damping apparatus for an automobile, it ispossible to suppress resonance phenomenon to thereby to have thevibration amplitude of the auxiliary mass within an appropriate range,and to realize ideal vibration suppression. As a result, the vibrationsuppression performance can be improved.

Next, a modified example of the damping apparatus shown in FIG. 17 isdescribed, with reference to FIG. 18. FIG. 18 is a block diagram showinga configuration of a modified example of the damping apparatus shown inFIG. 17. In this diagram, the same reference symbols are given tocomponents the same as those of the apparatus shown in FIG. 17, anddescriptions thereof are omitted. The apparatus shown in FIG. 18 differsfrom the apparatus shown in FIG. 17 in that, instead of thepredetermined value output section 68, there is provided a controlsection 69 that acquires excitation source information (excitationtiming, frequency, excitation force waveform, automobile body vibration,and so forth) and that outputs a command value for suppressingvibrations based on this excitation source information. A vibrationsuppression command value output by the control section 69 is generatedfrom the excitation force of the excitation source or frequencyinformation of the excitation force, and the vibration information orexcitation force information of an automobile body (damping targetdevice) 2, and output. The excitation section 30, based on thisvibration suppression command value, drives the linear actuator. Otheroperations are similar to the operations described above, and thedetailed descriptions thereof are therefore omitted.

The damping apparatus for an automobile according to the presentinvention is effective if attached to the body frame of the automobile,to in the vicinity of the engine mount or radiator, or to under part ofa rear luggage carrying section or trunk. By providing the low passfilters, the high frequency noise component can be removed, andtherefore generation of an abnormal noise caused by the noise componentcan be suppressed.

Moreover, the linear actuator provided within the excitation section 30is an actuator that uses electromagnetic force, and is effective if ituses a reciprocating motor for example. Furthermore, the actuatorprovided within the excitation section 30 may be a piezoelectricactuator that uses an element that causes displacement by applying avoltage thereto.

As described above, since there is provided a resonance suppressionmeans of the actuator based on the ideal actuator inverse characteristicthat uses the transfer function of the relative vibration velocity withrespect to the excitation force of the vibrating system of the actuator,it is possible to adjust the actuator characteristic to an arbitrarycharacteristic by setting the ideal actuator inverse characteristicbased on a desired characteristic. As a result, by increasing thedamping characteristic of the desired characteristic, it is possible toattain a characteristic such that resonance in the movable section ofthe actuator is unlikely to be generated by an external force that actson the actuator main unit. Therefore, it is possible to realize idealvibration suppression by generating an appropriate reaction force.Moreover, since it is possible to reduce the apparent natural frequencyof the actuator by reducing the natural frequency of the desiredcharacteristic, then even in the vicinity of the natural frequency ofthe actual actuator, it is possible to realize stable vibration controlwithout receiving the influence of the spring characteristic and thelike.

Seventh Embodiment

Next, a damping apparatus according to a seventh embodiment of thepresent invention is described, with reference to the drawing. FIG. 20is a block diagram showing a configuration of the same embodiment. Inthis diagram, reference symbol 30 denotes an excitation section that isfixed on a control target device 44, which is the target of dampingcontrol, and that drives an auxiliary mass member with a linear actuator(reciprocating motor) provided therein to thereby suppress thevibrations of the control target device 44. The control target device 44here refers to an automobile body for example.

Reference symbol 32 denotes an auxiliary mass (weight) attached to thecontrol target device 44. Reference symbol 34 denotes stators thatconstitute a reciprocating motor, and these stators 34 are fixed to thecontrol target device 44. Reference symbol 12 denotes a movable elementthat constitutes the reciprocating motor, and this movable elementreciprocates, for example, in the gravitational direction (in thevertical direction in FIG. 1). The excitation section 30 is fixed to thecontrol target device 44 so that the direction of the vibrations of thecontrol target device 44 to be suppressed matches the direction of thereciprocation (thrust direction) of the movable element 12. Referencesymbol 3 denotes a plate spring that supports the movable element 12 andthe auxiliary mass 32 while allowing them to move along the thrustdirection. Reference symbol 11 denotes a shaft that joins the movableelement 12 to the auxiliary mass 32, and is supported by the platespring 3. Reference symbol 35 denotes stoppers that limit the movablerange of the movable element 12, and limit the movable range on bothends of the movable element 12 (upper limit and lower limit in FIG. 20).

Reference symbol 620 denotes a command value generation section thatreceives the input of a state value (for example, engine revolutionspeed) of the control target device 44, and that calculates and outputsthe amplitude command value and frequency command value of thevibrations to be generated for the auxiliary mass 32. Reference symbol621 denotes an amplitude upper limit clamp table in which there isdefined the upper limit of applicable current value for each frequencythat is decided upon the amplitude command value and frequency commandvalue output from the command value generation section 620. Referencesymbol 622 denotes an application current generation section thatreceives the input of an amplitude command value and frequency commandvalue, that makes reference to the amplitude upper limit clamp table 621to perform correction for limiting the inputted amplitude command valuewithin an appropriate movable range, and that, based on the inputtedfrequency command and the amplitude command value after this correction(limitation) has been performed, finds and outputs a command value ofcurrent to be applied to the reciprocating motor. Reference symbol 72denotes a power amplifier that supplies current to the stator 34 of thereciprocating motor that constitutes the excitation section 30, and thatcontrols reciprocation of the movable element 12.

Next, an operation of the excitation section 30 shown in FIG. 20 isdescribed. In the case where an alternating current (sinusoidal current,square-wave current) is applied to a coil (not shown in the drawing)that constitutes the reciprocating motor, in a state where an current ina predetermined direction flows through the coil, magnetic flux is, inthe permanent magnet, guided from the south pole to the north pole,forming a magnetic flux loop. As a result, the movable element 12 movesin the direction opposite to that of gravity (upward direction). On theother hand, if a current in the direction opposite to that of thepredetermined direction flows through the coil, then the movable element12 moves in the gravitational direction (downward direction). Thedirection of the current flow into the coils is alternately changed bythe alternating current, and the movable element 12 thereby repeats theabove operation and reciprocates in the axial direction of the shaft 11with respect to the stator 34. Thus, the auxiliary mass 32 joined to theshaft 11 vibrates in the vertical direction. By controlling theacceleration of the auxiliary mass 32 based on control signals outputfrom the power amplifier 72, the control force is adjusted andvibrations of the control target device 44 can be reduced.

In the linear actuator shown in FIG. 20, rather than slidably andreciprocatably supporting the shaft 11, each of the plate springs 3supports the movable element 12 in two positions on the upper end sideand the lower end side of the shaft 11, and they elastically deformsthemselves to thereby support the movable element 12 while allowing itto reciprocate in the axial direction of the shaft 11. As a result, nowear or sliding resistance occurs on the movable element 12. Thereforeeven after use for a long period of time, the precision of the bearingsupport does not decrease, and a high level of reliability can beattained. Furthermore, there is no power consumption loss caused bysliding resistance, and an improvement in the performance can beachieved. However, as mentioned above, in the case where changes inbehavior of the automobile are significant as a result of suddenacceleration or traveling over rough road surface, changes in thecurrent supplied to the stators 34 also become more significant. As aresult, a phenomena where the movable element 12 collides with thestoppers 35 occurs. In the case of attaching the excitation section 30to an automobile as a damping apparatus, it is preferable that there beno sound of collision (abnormal noise) caused by collisions between themovable element 12 and the stoppers 35.

For this purpose, in the case where for each frequency of current beingapplied to the stators 34, an upper limit value of current that can benewly applied at the present moment is pre-found, the relationshipbetween this current frequency and the current upper limit value isstored in the amplitude upper limit clamp table 20, while replacing therelationship between them with the relationship between the amplitudecommand value and the frequency command value, and then the applicationcurrent generation section 622 finds a new application current commandvalue, this amplitude upper limit clamp table 20 is referenced, theamplitude command value output from the command value generation section620 is corrected, and based on this corrected amplitude command valueand the frequency command value output from the command value generationsection 620, a new application current command value is found to beoutput to the power amplifier 72. Thereby, it is possible to prevent themovable element 12 from colliding with the stoppers 35. Moreover, sinceamplitude command value correction is performed by making reference tothe table, the amount of calculation in the application currentgeneration section 622 can be reduced. Therefore, it is possible tospeed up the processing while allowing use of an inexpensive calculationapparatus to achieve a reduction in the cost.

Next, a modified example of the damping apparatus shown in FIG. 20 isdescribed, with reference to FIG. 21. In this diagram, the samereference symbols are given to components the same as those of theapparatus shown in FIG. 20, and descriptions thereof are omitted. Theapparatus shown in this diagram differs from the apparatus shown in FIG.20 in that instead of the amplitude upper limit clamp table 621, thereis provided a current upper limit clamp table 623. The current upperlimit clamp table 623 is a table such that for each frequency of currentbeing applied to the stators 34, an upper limit value of current thatcan be newly applied at the present moment is pre-found, and therelationship between this current frequency and the current upper limitvalue is pre-stored, while replacing the relationship between them withthe relationship between the application current command value and thefrequency command value. In the case where the application currentgeneration section 622 finds a new application current command value,this current upper limit clamp table 623 is referenced, and based on theamplitude command value output from the command value generation section620 and the frequency command value output from the command valuegeneration section 620, the newly found application current commandvalue is corrected and output to the power amplifier 72. Thereby, it ispossible to prevent the movable element 12 from colliding with thestoppers 35.

Eighth Embodiment

Next, with reference to FIG. 22, a damping apparatus according to aneighth embodiment of the present invention is described. FIG. 22 is ablock diagram showing a configuration of the same embodiment. In thisdiagram, the same reference symbols are given to components the same asthose of the apparatus shown in FIG. 20, and descriptions thereof areomitted. This apparatus shown in FIG. 22 differs from the apparatusshown in FIG. 20 in that instead of the amplitude upper limit clamptable 621, there is provided a gradient limiting section 625, and anapplication current generation section 624 finds an application currentcommand value based on the amplitude command value in which the gradientof amplitude changes is limited by the gradient limiting section 625.The gradient limiting section 625 is for turning the gradient of changesin an inputted amplitude command value into gradual changes to beoutput. In the case where the application current generation section 624finds a new application current command value, based on an amplitudecommand value in which the gradient of changes is limited by thegradient limiting section 625 and a frequency command value output fromthe command value generation section 620, a new application currentcommand value is found and output to the power amplifier 72, and therebysudden changes in application current can be suppressed. As a result, itis possible to prevent the movable element 12 from colliding with thestoppers 35. Moreover, by providing limitation only in the case wherefrequency changes are significant, it is possible to reduce responsedelays.

Next, a modified example of the damping apparatus shown in FIG. 22 isdescribed, with reference to FIG. 23. In this diagram, the samereference symbols are given to components the same as those of theapparatus shown in FIG. 22, and descriptions thereof are omitted. Theapparatus shown in this diagram differs from the apparatus shown in FIG.22 in that the gradient limiting section 626 is provided on thesubsequent stage of the application current generation section 624. Thegradient limiting section 626 has a function equal to that of the lowpass filter, and receives the input of the application current commandvalue found by the application current generation section 624, and turnsthe gradient of changes in this inputted application current commandvalue into gradual changes to be output. The gradient of changes in theapplication current command value newly found by the application currentgeneration section 624 is corrected to be gradual and output to thepower amplifier 72, and thereby sudden changes in application currentcan be suppressed. Therefore, it is possible to prevent the movableelement 12 from colliding with the stoppers 35.

Ninth Embodiment

Next, with reference to FIG. 24, a damping apparatus according to aninth embodiment of the present invention is described. FIG. 24 is ablock diagram showing a configuration of the same embodiment. In thisdiagram, the same reference symbols are given to components the same asthose of the apparatus shown in FIG. 20, and descriptions thereof areomitted. This apparatus shown in FIG. 24 differs from the apparatusshown in FIG. 20 in that instead of the amplitude upper limit clamptable 621, there is provided an amplitude suppression section 627 and achange detection section 629, and an application current generationsection 628 finds an application current command value based on theamplitude command value whose amplitude is limited by the amplitudesuppression section 627. The amplitude suppression section 627suppresses changes in amplitude command values, according to the changeamount of the frequency command value detected by the change detectionsection 629. The change detection section 629 constantly detects changesin the frequency command value output from the command value generationsection 620, and in the case where the change amount exceeds apredetermined value, notifies the amplitude suppression section 627 thatthe change amount has exceeded the predetermined value. In the casewhere the application current generation section 628 finds a newapplication current command value, then based on an amplitude commandvalue whose amplitude is limited by the amplitude suppression section627 based on the frequency changes detected by the change detectionsection 629, and a frequency command value output from the command valuegeneration section 620, a new application current command value is foundand output to the power amplifier 72, and thereby sudden changes inapplication current can be suppressed. As a result, it is possible toprevent the movable element 12 from colliding with the stoppers 35.Moreover, by appropriately controlling the amount of amplitudesuppression with the amplitude suppression section 627, it is stillpossible to continue driving to a certain degree even when suddenfrequency changes occur.

Next, a modified example of the damping apparatus shown in FIG. 24 isdescribed, with reference to FIG. 25. In this diagram, the samereference symbols are given to components the same as those of theapparatus shown in FIG. 24, and descriptions thereof are omitted. Theapparatus shown in this diagram differs from the apparatus shown in FIG.24 in that instead of the amplitude suppression section 627, there isprovided a current suppression section 630. The current suppressionsection 630 suppresses changes of the application current command valuefound by the application current generation section 628 in the casewhere the change amount of the frequency command value detected by thechange detection section 629 has exceeded a predetermined value. In thecase where the change amount of the frequency command value output fromthe command value generation section 620 has exceeded the predeterminedvalue, an application current command value newly found by theapplication current generation section 628 is corrected so as tosuppress changes, and is output to the power amplifier 72. Thereby,sudden changes in application current can be suppressed, and thereforeit is possible to prevent the movable element 12 from colliding with thestoppers 35.

As described above, in the case of controlling current to be applied tothe actuator (reciprocating motor) based on the amplitude command valueand frequency command value of vibrations to be generated, the value ofcurrent to be applied to the actuator is limited so that the vibrationamplitude of the auxiliary mass 32 does not exceed a predeterminedvalue. Therefore, it is possible to constantly drive the movable elementof the actuator within an appropriate movable range. Thus, collisionbetween the movable element 12 and the stoppers 35 is eliminated, andtherefore generation of collision sound can be suppressed. Furthermore,since control of the application current value enables constant drivingof the movable element of the actuator within an appropriate movablerange, the stoppers 35 provided within the actuator (reciprocatingmotor) are no longer required, and it is possible to simplify thestructure of the actuator.

A program for realizing the respective functions may be recorded on acomputer-readable recording medium, and the program recorded on thisrecording medium may be loaded and executed on a computer system tothereby perform vibration suppression control. The “computer system”here includes an OS (operation system) and hardware such as peripheraldevices. Moreover, the “computer-readable recording medium” refers to atransportable medium such as flexible disc, magnetic optical disc, ROM,and CD-ROM, or a recording device such as built-in hard disk of acomputer system. Furthermore, the “computer-readable recording medium”includes a medium that holds a program for a certain period of time, andexamples of such recording medium include built-in volatile memory (RAM)of a computer system serving as a server or client in the case where theprogram is transmitted via a network such as the Internet or acommunication line such as a telephone line.

Moreover, the above program may be transmitted from a computer systemhaving this program stored in a storage device or the like, to anothercomputer system via a transmission medium or transmission waves in thetransmission medium. Here the “transmission medium” for transmitting theprogram refers to a medium having a function of transmittinginformation, such as networks such as the Internet (communicationnetworks) or communication circuits such as telephone lines(communication lines). Also, the above program may be a program forrealizing part of the function described above. Furthermore, the aboveprogram may be a so-called differential file (differential program) thatcan be realized by combining the above described functions with theprogram pre-recorded on the computer system.

INDUSTRIAL APPLICABILITY

In the above description, the description has been for where the dampingtarget is an automobile body. However, the damping target device of thepresent invention does not always have to be an automobile body, and itmay be an autonomous traveling carrier, a robot arm, and so forth.

1. (canceled)
 2. A damping apparatus for an automobile that reducesvibrations of an automobile body, comprising: an actuator that isattached to the automobile body and drives an auxiliary mass; a springelement that supports the auxiliary mass so as to be able to move in adrive direction of the actuator; a current detector that detects acurrent flowing through an armature of the actuator; a section thatdetects a terminal voltage applied to the actuator; a calculationcircuit that calculates an induced voltage of the actuator, and furthercalculates a relative velocity of the actuator, based on a currentdetected by the current detector and the terminal voltage; and a controlcircuit that superimposes a damping characteristic based on a relativevelocity calculated by the calculation circuit, and controls theactuator.
 3. The damping apparatus for an automobile according to claim2, wherein the calculation circuit calculates the induced voltage,limited to a band in a vicinity of a frequency of a natural vibration ofthe actuator.
 4. The damping apparatus for an automobile according toclaim 3, wherein the calculation circuit includes a band-pass filterthat limits to a band in the vicinity of the frequency of the naturalvibration of the actuator.
 5. The damping apparatus for an automobileaccording to claim 4, wherein the band-pass filter is set so that aphase in the vicinity of the frequency of the natural vibration of theactuator becomes 0 degrees.
 6. The damping apparatus for an automobileaccording to claim 4, wherein the calculation circuit further includes alow-pass filter with a cutoff frequency that is higher than thefrequency of the natural vibration of the actuator. 7-14. (canceled) 15.A control method for reducing vibrations of an automobile body,comprising the steps of: detecting a current flowing through an armatureof an actuator that is attached to the automobile body and drives anauxiliary mass; detecting a terminal voltage applied to the actuator;calculating an induced voltage of the actuator, and further calculatinga relative velocity of the actuator, based on the detected current andthe detected terminal voltage; and superimposing a dampingcharacteristic based on the calculated relative velocity of theactuator, and drive-controlling the actuator.
 16. The control method forreducing vibrations of an automobile body according to claim 15, whereinthe induced voltage is calculated, limited to a band in a vicinity of afrequency of a natural vibration of the actuator. 17-59. (canceled)